This invention relates to bearing materials and more particularly to an improved low friction bearing material and method and elements formed therefrom having excellent resistance to wear and which can be easily fabricated.
Bearing compositions containing as an element thereof a fluorocarbon resin, such as polytetrafluoroethylene polymers are known in the art to produce low friction bearing elements which, because of the presence of the fluorocarbon resin, normally require no other lubrication to provide a low friction surface between moving parts. Polytetrafluoroethylene resin, although classified as thermoplastic is difficult and expensive to fabricate. Customary methods of fabrication such as injection molding and melt extrusion, cannot be applied to polytetrafluoroethylene and generally solid shapes formed from polytetrafluoroethylene are fabricated by cold forming operations followed by sintering.
In an attempt to avoid the costly cold forming and sintering techniques, compositions have been developed which combine polytetrafluoroethylene and other more easily fabricated resins. The purpose of such compositions is to combine the low friction of polytetrafluoroethylene with the ease of fabrication of the resin with which it is combined. Examples of such compositions, which incorporate fluorocarbon resins, can be seen in U.S. Pat. Nos. 3,287,288, Relling and 2,998,397, Riesing. Although the compositions of Relling and Riesing can be used to produce low friction bearing elements by injection molding techniques, the finished bearing elements demonstrate poor wear characteristics and are, thus, not particularly suited for heavy duty application.